Study On The Construction And Properties Of Surfaces With Micro/nano Fine Structures

Wettability of the solid surface is the important properties of solid surface, and also one of common interfacial phenomena, which mainly depends on both their chemical composition and geometrical structure. It not only directly affects various life activities of plants and animals in nature, but also plays important roles in high-tech fields and daily life. Especially, superhydrophobic surfaces with antifouling and self-cleaning properties have received more and more attention, and become a hot topic of surface functional materials recently. However, there are some serious problems limitting the real application of superhydrophobic materials, such as complicated process, high cost, poor stability, and low external stimuli-sensitivity. In the present thesis, different techniques have been employed to construct micro/nano structures on surfaces of a variety of materials, resulting in the generation of surfaces with superhydrophobic properties. Surface wettability has been tuned by efficient control of microstructure and composition of the surfaces. The main results are shown as follows:1. Through adding acetone in PP solution, the polypropylene (PP) surfaces with micro/nano hierarchical structures are successfully fabricated by the control of surface crystalline morphology via the solvent/nonsolvent method. The resulting surfaces present superhydrophobicity without any chemical modification. The optimal water contact angle and sliding angle of the superhydrophobic PP surface obtained are observed to be 160°and 4°, respectively. It is shown from stability experiments that the superhydrophobic PP surfaces exhibit excellent chemical stability and environmental stability.2. The superhydrophobic PP/TiO2 surfaces have been obtained by addition of TiO2 nanoparticles into the polypropylene solution. The as-prepared surfaces have petal-like micro/nano-binary structures similar to those of lotus leaves. Its water contact angle and sliding angle are observed to be 169°and 4°, respectively. The stability of as-prepared PP/TiO2 surfaces is also investigated and the results show the PP/TiO2 surfaces maintain superhydrophobicity under either acidic or basic conditions. Reversible switching between superhydrophobicity and hydrophobicity on PP/TiO2 surface has been obtained by the alternation of UV irradiation and dark storage.3. Superhydrophobic polysterene (PS) films with super-adhesive effects have been constructed by the solvent/nonsolvent method. Without any chemical modification, the water contact angle of the resulting PS surface reaches to 153°. A water droplet on the film cannot move at any tilt angle even when the substrate is turned upside down, which provides posibility of its application on the no-loss liquids transportation. The reason of high adhesive force about as-prepared PS surface has also been explained. It is proposed that the nature of polysterene and its micro/nano-sphere structures are both responsible for high adhesive forces between water droplets and superhydrophobic PS surface.4. The superhydrophobic PS/TiO2 surfaces have been created by the addition of TiO2 nanoparticles into the polystyrene solution. The water contact angles of the PS/TiO2 surfaces increase with the temperature. When the drying temperature is 180℃, the water contact angle of the PS/TiO2 surface is up to 163°, which is due to the change of surface structures and composition caused by TiO2 nanoparticles and solvent evaporation, respectively. The effect of UV irradiation on the wettability of the as-prepared PS/TiO2 surface has been investigated and the results show that the PS/TiO2 surface changes from superhydrophobicity to superhydrophilicity by UV irradiation. After the UV-irradiated film is put in the dark for 15 d, its wettability recovers to the pristine superhydrophobic state. In one word, reversible switching between superhydrophobicity and superhydrophilicity can be obtained by alternating UV irradiation and dark storage.5. The microflower and nanorod hierarchical structures are fabricated on copper substrates by a wet chemical reaction. After chemical modification with stearic acid, the resulting surface exhibits superhydrophobicity with a water contact angle of 175°and a sliding angle of 5°. The lotus-leaf-like structure is an ideal structure for the fabrication of superhydrophobic surface with a low contact angle hysteresis. Interestingly, the wettability reversible transition between superhydrophobicity and superhydrophilicity can be realized on the as-fabricated copper surfaces by the alternation of air-plasma and stearic coating.6. The rough aluminum surfaces textures composed of protrusion, pores and nanoflakes have been created by HC1 etching and boiling water treatment. After chemical modification with pentadecafluorooctanoic acid, the resulting surfaces exhibit superhydrophobicity and low contact angle hysteresis. The stability experiments show that the as-fabricated aluminum surfaces are still superhydrophobic on contact with acid or base. Furthermore, the aluminum surface can be switched from superhydrophobicity to superhydrophilicity quickly by the air-plasma treatment. However, when plasma-treated surfaces are immersed into the pentadecafluorooctanoic acid solution, the superhydrophobicity of the surface can be obtained again. It is indicated that wettability transition of the surface fabricated is reversible.7. The superhydrophobic surfaces on glass substrates are prepared via a wet chemical synthetic route and chemical modification. The as-prepared glass surfaces show a high water contact angle of 155°and a low sliding angle of 8°. The superhydrophobicity may result from combination of the vine-like fine structure fabricated and the modification of vinyltriethoxysilane. It is shown from stability experiments that superhydrophobic glass surfaces display excellent chemical stability and environmental stability.